Monitoring system for voltage tunable receivers and converters utilizing voltage comparison techniques

Abstract

A system for remotely monitoring or determining the channel to which a voltage tunable receiver (or CATV converter) has been tuned includes an encoder for measuring the magnitude of the tuning voltage applied to the tuning section of the receiver and for generating a channel representative digital code in response to the tuning voltage. The digital code thus generated is compatible with remotely located monitoring equipment, and represents the number of the channel to which the receiver is tuned. Since the tuning voltage is not linearly related to the channel number of the station being received, the encoder utilizes a read-only memory or the like for storing a coded representation relating the channel number to the tuning voltage. In a preferred embodiment, the coded representations are sequentially stored as tuning voltage representations in address locations of the memory corresponding to the respective channel numbers. The read-only memory locations are sequentially addressed, and the tuning voltage representations are compared with the amplitude of the tuning voltage currently being applied to the receiver. When the value of the tuning voltage representation equals or exceeds the amplitude of the tuning voltage, the sequential addressing is terminated and the address of the last accessed memory location is stored to provide a coded indication of the channel number of the station being received.

What is claimed and desired to be secured by Letters Patent of the United States is: 
     
       1. Apparatus for determining at a central location the channel to which a remotely located receiver tunable to a plurality of channels by a tuning voltage has been tuned comprising: means for sequentially generating a plurality of digital indications of numbers identifying said channels;   means responsive to said channel number digital indication generating means for sequentially generating a plurality of coded representations of voltages, each said coded representations corresponding to one of said digital indications and being nonlinearly related to said digital indications;   means for sequentially comparing each of said coded representations with the tuning voltage applied to said receiver;   means responsive to said sequentially comparing means for generating a digital code representative of the digital indication corresponding to the coded representation representing a voltage having an amplitude within a predetermined range of amplitudes relative to the amplitude of the tuning voltage applied to said receiver; and   means for transmitting said digital code to the central location.   
     
     
       2. Apparatus as recited in claim 1 wherein said coded representation generating means includes a memory having a plurality of storage locations for storing said coded representations of voltages therein. 
     
     
       3. Apparatus as recited in claim 2 wherein said memory includes a programmable read-only memory. 
     
     
       4. Apparatus as recited in claim 2 wherein said channel number digital indication generating means includes a clock producing timing signals and a counter operatively coupled to said clock and counting said timing signals, the count in said counter being representative of both one of said storage locations and the channel number digital indication corresponding to said one of said storage locations. 
     
     
       5. Apparatus as recited in claim 4 wherein said digital code generating means includes means operatively coupled to said counter for providing an output signal representative of the count present in said counter when the value of the coded representation of voltage stored in the addressed memory location is within said predetermined range of values relative to the amplitude of said tuning voltage. 
     
     
       6. Apparatus as recited in claim 5 wherein said digital code generating means includes an output register. 
     
     
       7. Apparatus as recited in claim 5 wherein said sequentially comparing means includes means responsive to said coded representations of voltage for providing an analog signal having an amplitude proportional to the value of said coded representations of voltage and means for comparing the amplitude of said analog signal and the amplitude of said tuning voltage, said output signal providing means being responsive to said amplitude comparing means for providing said count representative output signal when the amplitude of said analog signal is within a predetermined range of amplitudes relative to the amplitude of said tuning voltage. 
     
     
       8. Apparatus as recited in claim 7 wherein said analog signal providing means includes a digital-to-analog converter and wherein said comparing means includes an analog comparator. 
     
     
       9. Apparatus as recited in claim 5 wherein said sequentially comparing means includes means responsive to the amplitude of said tuning voltage for providing a digital signal representative of the amplitude of said tuning voltage and means for comparing the values of said tuning voltage representative digital signal and said coded representations of voltage, said output signal providing means being responsive to said values comparing means for providing said count representative output signal when the values of said tuning voltage representative digital signal are within a predetermined range of values relative to the values of said coded representation of voltage. 
     
     
       10. Apparatus as recited in claim 9 wherein said tuning voltage representative digital signal providing means includes an analog-to-digital converter and wherein said values comparing means includes a digital comparator. 
     
     
       11. A method for determining the channel to which a remotely located voltage tunable receiver is tuned comprising the steps of: monitoring the amplitude of the tuning voltage applied to the voltage tunable receiver;   sequentially generating a plurality of digital indications, each representative of a channel number;   generating a coded representation of voltage in response to each channel number digital indication, each coded representation corresponding to a voltage operative to tune said receiver to a respective channel, said coded representations being nonlinearly related to said digital indications;   comparing each of said coded representations with the tuning voltage applied to the receiver;   generating a digital code representative of the channel to which the receiver is tuned when said coded representation has a predetermined relationship to said tuning voltage; and   transmitting an indication of the channel representative digital code to a central location.   
     
     
       12. A method as recited in claim 11 wherein the step of comparing each of said coded representations with the tuning voltage applied to the receiver includes the steps of: generating a coded representation of the tuning voltage applied to the receiver; and   comparing the values of said coded representation of said tuning voltage and the generated representations of voltage.   
     
     
       13. The method as recited in claim 11 wherein the step of generating the plurality of digital indications includes the steps of generating a plurality of timing signals, counting the timing signals to provide a variable count signal, the count in said count signal being representative of a channel to which the receiver is tuned; and the step of generating the plurality of coded representations of voltage includes the step of addressing a memory circuit which said counter, each count in the counter defining a unique address location having one of said representations of voltage stored therein.   
     
     
       14. A method as recited in claim 13 wherein the step of comparing each of said coded representations with the tuning voltage applied to the receiver includes the steps of: providing an analog voltage proportional to the tuning voltage applied to the receiver;   providing an analog voltage having an amplitude proportional to the value of the coded representation of voltage in the addressed memory location; and   comparing the amplitudes of the tuning voltage representative signal and the analog voltage representative of the coded representation stored in the addressed memory location.   
     
     
       15. A method as recited in claim 14 wherein the step of generating the digital code representative of the channel includes the step of sampling the count in said counter when the tuning voltage and the analog voltage have substantially similar amplitudes.